Open Mobile Alliance (OMA) Digital Rights Management (DRM) is a technology that allows control over the consumption of various media objects, such as ring tones, images, and other objects, by mobile terminals. DRM is a term used to describe a range of techniques that use information about rights and rights holders to manage copyright material and the terms and conditions on which the material is made available to users. More specifically, DRM involves the description, layering, analysis, valuation, trading, and monitoring of an owner's property rights to an asset. DRM covers the management of the digital rights to the physical manifestation of a work (e.g., a textbook) or the digital manifestation of a work (e.g., an Internet web page). DRM also covers the management of an asset whether the asset has a tangible or an intangible value. Current DRM technologies include languages for describing the terms and conditions for an asset, tracking asset usage by enforcing controlled environments or encoded asset manifestations, and closed architectures for the overall management of the digital rights. In OMA DRM technology, control is exercised by supplementing each media object with a rights object. The rights object defines rules according to which the media object is consumed.
OMA DRM technology is by used many mobile terminals for the protection of content images, sound files, videos, and other items. Unprotected files are stored in the file system in a plain text format, while protected files are encrypted. Then, it is assumed that whenever an application requests the content of a protected file, the DRM agent (a special system component) decrypts the file on the fly and provides the data to the requesting application. At the same time, an application can usually use a special API to read the same protected file in the encrypted form, bypassing the DRM agent.
Unfortunately, the access method described above is not always possible. This is because some APIs, such as Java APIs, were initially created without taking OMA DRM protection of content into account. This has resulted in a dilemma. When a Java application requests the content of an OMA DRM protected file, it is unclear whether the file's data should be passed to an application as is (i.e., encrypted), or whether the DRM agent should perform decryption beforehand. Currently, some Java applications, such as image viewers and music players, require protected files in plain text form. Other Java applications, however, such as file managers and electronic mail clients require protected files in encrypted form. Moreover, certain applications may require both types of access. For example, some image viewers may be able both to display OMA DRM protected images and to superdistribute them.
The situation discussed above is further complicated by the fact that the same Java application can use different Java APIs to open the same protected file. For example, Multimedia API (JSR 135) may play a music file, while File API (JSR 75) is used to copy it. In addition and, with regard to the OMA DRM protection of files, all Java APIs fall (with certain reservations) into one of two categories: “safe” APIs that do not allow an application to get hold of a protected file's content; and “unsafe” APIs that allow an application to do so.
There is therefore a need for a system that will allow an application to specify the form in which the protected file's content is to be read. This mechanism should be universal enough to be usable in virtually any Java APIs that can potentially access protected files as well as other APIs.